AIRS is the infrared spectroscopic instrument of ARIEL: Atmospheric Remote‐sensing Infrared Exoplanet Large‐survey mission adopted in November 2020 as the Cosmic Vision M4 ESA mission and planned to be launched in 2029 by an Ariane 6 from Kourou toward a large amplitude orbit around L2 for a 4-year mission. Within the scientific payload, AIRS will perform transit spectroscopy of over 1000 exoplanets to complete a statistical survey, including gas giants, Neptunes, super-Earths and Earth-size planets around a wide range of host stars. All these collected spectroscopic data will be a major asset to answer the key scientific questions addressed by this mission: what are exoplanets made of? How do planets and planetary systems form? How do planets and their atmospheres evolve over time? The AIRS instrument is based on two independent channels covering 1.95-3.90 µm (CH0) and 3.90-7.80 µm (CH1) wavelength ranges with prism-based dispersive elements producing spectra of low resolutions R>100 in CH0 and R>30 in CH1 on two independent detectors. The spectrometer is designed to provide a Nyquist-sampled spectrum in both spatial and spectral directions to limit the sensitivity of measurements to the jitter noise and intra pixels pattern during the long (10 hours) transit spectroscopy exposures. A full instrument overview will be presented covering the thermo-mechanical design of the instrument functioning in a 60 K environment, up to the detection and acquisition chain of both channels based on 2 HgCdTe detectors actively cooled to below 42 K. This overview will present updated information of phase C studies, in particular on the assembly and testing of prototypes that are highly representative of the future engineering model that will be used as an instrument-level qualification model.
In this communication, we report on electrical and electro-optical characterizations of InAs/InAsSb Type-II superlattice (T2SL) MWIR photodetector, showing a cut-off wavelength at 5 μm. The device, made of a barrier structure in XBn configuration, was grown by molecular beam epitaxy (MBE) on GaSb substrate. At 150K, dark current measurements shows a device in the Shockley-Read-Hall (SRH) regime but with an absolute value comparable to the state-of-the-art. A quantum efficiency of 50% at the wavelength of 3 μm for a 3 μm thick absorption layer is found in simple pass configuration and front-side illumination. Combined with lifetime measurements performed on dedicated samples through time resolved photoluminescence (TRPL) technique, mobility is extracted from these measurements by using a theoretical calculation of the quantum efficiency thanks to Hovel’s equations. Such an approach helps us to better understand the hole minority carrier transport in Ga-free T2SL MWIR XBn detector and therefore to improve its performance.
In this paper, we study the influence of three different etching depths on electrical and electro-optical properties of nonpassivated T2SL nBn Ga-free pixel detector having a 5μm cut-off wavelength at 150 K. The study shows the strong influence of lateral diffusion length on the shallow etched pixel properties and therefore, the need to perform etching through the absorber layer to avoid lateral diffusion contribution. The lowest dark current density was recorded for a deep-etched detector, on the order of 1 × 10-5 A/cm2 at 150 K and operating bias equal to – 300 mV. The quantum efficiency of this deep-etched detector is measured close to 55 % at 150 K, without anti-reflection coating. A comparison between electro-optical performances obtained on the three etching depths demonstrates that the etching only through the middle of the absorber layer (Mid-etched) allows eliminating lateral diffusion contribution while preserving a good uniformity between the diode’s performance. Such result is suitable for the fabrication of IR focal plane arrays (FPA).
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